The present invention generally regards monitoring vehicle data collected from an accelerometer. More particularly, the present invention regards a method and system for monitoring tire pressure and tire parameters using an accelerometer mounted near a wheel.
Significant effects on the tire/wheel/suspension ensemble and overall driving safety may be caused by any of tire deflation or underinflation; tire tread wear, separation, or aging; suspension aging and failure; external ambient conditions (e.g., temperature, humidity); and wheel imbalance. Several systems have been developed to monitor tire pressure in particular, including both direct and indirect systems.
Direct measurement systems include pressure sensors and temperature sensors mounted in the tire in which the signals are wirelessly transmitted to a control unit. The disadvantages of such a system are that it may require batteries, which can cause failure when the batteries fully discharge, problems at low temperatures, and disposal problems. There may be communication problems arising in such a system due to the difficulty of distinguishing the signals received from different tires due to the wireless connections. Additionally, ESD (electrostatic dischage) problems may develop in such a system.
Indirect systems available include algorithms using ABS sensor signals such as wheel speed and inertial sensors. Various problems may be associated with these indirect measurement systems. For instance, some driving conditions may not produce significant information. Also, accuracy may potentially be reduced during new tire brake-in or after a tire change. Additional sensor signals from active dampers (e.g., vertical displacement sensors) may be used in indirect monitoring systems to increase accuracy, and may utilize dynamic frequency evaluation of wheel speed sensors using Fast Fourier Transforms (FFTs). However, there may be insufficient excitation on smooth roads to yield good data utilizing this method. Additionally, there is still significant imprecision with this method and potentially anomalous readings may yield insufficient information to form a conclusion.
Therefore, what is needed is a method for measuring tire pressure, tire tread condition, suspension condition, and other vehicle dynamics using sensors already on many vehicles (including wheel rotation speed sensors), systems already present in some vehicles (electronic stability programs (ESP) and anti-lock braking systems (ABS)), and low-cost additional sensors that increase accuracy by measuring missing dynamics.
A method is provided for monitoring an operating condition of a vehicle including the steps of measuring a longitudinal, a lateral, and/or a vertical acceleration, as well as a wheel rotation speed. The method involves determining a tire condition, a wheel condition, and/or a suspension condition from the wheel rotation speed and the longitudinal, the lateral, and/or the vertical acceleration. Two methods of data analysis are provided which may be utilized alone or in combination. The methods are on-line model-based observers (on-line estimators) and data-based signal processing using power spectral methodologies (one possible method is monitoring Fast Fourier Transforms (FFTs) envelopes).
A device is provided including an accelerometer at a wheel of a vehicle, a wheel rotation speed sensor, and a microprocessor for determining an operating condition. The accelerometer measures a longitudinal, a lateral, and/or a vertical acceleration. The wheel rotation speed sensor measures a rotation speed of the wheel. The microprocessor is electrically coupled to the accelerometer and the wheel rotation speed sensor.
A system is provided for monitoring an operating condition of a vehicle which includes an accelerometer (one-dimensional, two-dimensional, or three-dimensional) for each wheel of the vehicle at an axle-end. Each of the accelerometers measures a longitudinal, a lateral, and/or a vertical acceleration. A wheel rotation speed sensor for each wheel of the vehicle is arranged at an axle-end and measures a rotation speed for each wheel. A microprocessor determines the operating condition, which may include a tire condition, a wheel condition, and/or a suspension condition. The microprocessor is electrically coupled to each of the accelerometers and each of the wheel rotation speed sensors.
The advantages of the present invention are that there may be sufficient excitation of the sensor systems from a normal tire tread and proper inflation on even a smooth road. No wireless connection may be necessary, and therefore there may be fewer communication problems and therefore better data and increased accuracy. The accelerometer(s) may be integrated with the wheel rotation speed sensors already used for ABS. The signals may be transmitted over the same output as the wheel rotation speed sensor by modulating the signal or by any other appropriate method of simultaneous signal transmission. This may avoid additional mounting and wiring and the costs associated therewith.